Information AboutTriac |
| CATEGORIES ABOUT TRIAC | |
| solid state switches | |
| power electronics | |
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A TRIAC, or '''TRIode for Alternating Current''' is an Electronic component approximately equivalent to two Silicon-controlled Rectifier s (SCRs/ Thyristor s) joined in Inverse Parallel (paralleled but with the polarity reversed) and with their gates connected together. This results in a bidirectional electronic switch which can conduct Current in either direction when it is triggered (turned on). It can be triggered by either a positive or a negative Voltage being applied to its ''gate'' electrode. Once triggered, the device continues to conduct until the current through it drops below a certain threshold value, such as at the end of a half-cycle of Alternating Current (AC) mains power. This makes the TRIAC a very convenient switch for AC circuits, allowing the control of very large power flows with Milliampere -scale control currents. In addition, applying a trigger pulse at a controllable point in an AC cycle allows one to control the percentage of current that flows through the TRIAC to the load (so-called ''phase control''). Low power TRIACs are used in many applications such as Light Dimmer s, speed controls for Electric Fan s and other Electric Motor s, and in the modern computerized control circuits of many household Small and Major Appliance s. However, when used with Inductive loads such as electric fans, care must be taken to assure that the TRIAC will turn off correctly at the end of each half-cycle of the ac power. A Snubber circuit is often used to assist this turn off. Snubber circuits are also used to prevent premature triggering. For higher-powered, more-demanding loads, two SCRs in inverse parallel may be used instead of one TRIAC. Because each SCR will have an entire half-cycle of reverse polarity voltage applied to it, turn-off of the SCRs is assured, no matter what the character of the load. SEE ALSO EXTERNAL LINKS |
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